Catalytic cracking is a petroleum refining process that is applied commercially on a very large scale. A majority of the refinery petroleum products are produced using the fluid catalytic cracking (FCC) process. An FCC process typically involves the cracking of heavy hydrocarbon feedstocks to lighter products by contacting the feedstock in a cyclic catalyst recirculation cracking process with a circulating fluidizable catalytic cracking catalyst inventory consisting of particles having a mean particle size ranging from about 50 to about 150 μm, preferably from about 50 to about 100 μm.
The catalytic cracking occurs when relatively high molecular weight hydrocarbon feedstocks are converted into lighter products by reactions taking place at elevated temperature in the presence of a catalyst, with the majority of the conversion or cracking occurring in the vapor phase. The feedstock is converted into gasoline, distillate and other liquid cracking products as well as lighter gaseous vaporous cracking products of four or less carbon atoms per molecule. The vapor partly consists of olefins and partly of saturated hydrocarbons. The products also include bottoms and coke deposited on the catalyst during hydrocarbon cracking. It is desirable to produce the lowest bottoms at a constant coke level.
FCC catalysts normally consist of a range of extremely small spherical particles. Commercial grades normally have average particle sizes ranging from about 45 to 150 μm, preferably from about 55 to about 150 μm. FCC catalysts are generally composed of zeolite, matrix, clay and binder. The cracking catalysts may be comprised of a number of components incorporated into a single particle or may be comprised of blends of individual particles having different functions.
Rare earth metals have been widely used as a component of FCC catalyst to provide catalysts having enhanced activity and hydrothermal zeolite stability with increased yield performance. The level of rare earth metals in a specific catalyst formulation is determined by operational severity and product objectives. However, the need for increased amounts of gasoline and the need to process heavy crudes containing high metal contents have led to an increase in the level of rare earths in their FCC catalyst formulations over time. The amount of rare earth metal typically used in the FCC catalyst ranges from about 0.5 to about 6 wt % of the total FCC catalyst formulations.
Recently, China, which produces 95% of the world's supply of rare earth metals, has severely cut its export of precious rare earth metals, causing a troubling increase in catalyst costs. The refining industry has instinctively reacted by opting for lower rare earth catalyst formulations to offset costs of the raw materials. Such action offers immediate and successful cost savings. However, reduced rare earth levels can have a significant impact on catalyst performance, e.g. in reduced catalyst activity, stability and yields, thereby affecting bottom-line profit generation.
Consequently, there exists a need in the FCC refining industry for rare earth free catalytic cracking catalysts that provide a catalytic activity and selectivity comparable to or improved over conventional rare earth containing FCC catalysts during a catalytic cracking process.